German patent application DE 100 56 820 A1 discloses a contact system for each pole of a power circuit breaker having a rotary contact bridge that electrically connects or disconnects two fixed contacts that are positioned across from each other. The rotary contact bridge is float-mounted in a breaker shaft segment by means of two contact force springs configured as pressure springs. The contact force springs are mounted across from each other on both sides of the rotary contact bridge in bores made in the breaker shaft and, through their free spring ends fitted with sliding elements, are constantly interacting with control cams of the rotary contact bridge. When the control cams are appropriately configured, the rotary contact bridge, the contact force springs and the breaker shaft segment form a tilting snap-action mechanism. When the rotary contact bridge is electrodynamically repulsed from the fixed contacts due to a short-circuit current flowing through the contact system, the free spring ends slide along the control cams with increasing compression of the contact force springs until, after passing the tilting point of the tilting snap-action mechanism, they move into latching depressions of the control cams. As a result, the rotary contact bridge remains in the repulsed position until it is deliberately moved away from this position by means of an actuating mechanism. A drawback of this is the unsatisfactory reproducibility of the dynamic tilting behavior of the contact system due to the frictional work that occurs between the pins and the control cams, due to the compressive forces on the free spring ends that are not directed towards the tilting axis and due to the tangential forces that act upon the sliding elements.
German patent specification DE 42 22 965 C1 discloses a contact system for each pole of a power circuit breaker having a single-arm contact lever that connects or disconnects a fixed contact and a connecting lead that is electrically connected to the contact lever in a tilting axis. The contact lever that is mounted along the tilting axis on a breaker shaft is impinged on both sides by a pair of contact force tension springs. These tension springs are suspended between the contact lever and the breaker shaft beyond the tilting axis in such a way that, together with the contact lever and the breaker shaft, they form a tilting snap-action mechanism. When the contact lever is electrodynamically repulsed from the fixed contact, the two connection straight lines run through the tilting axis of the tilting snap-action mechanism in the tilting point—also referred to as the dead center—and, at this moment, said straight lines forming the tilting point plane, which can also be called the dead center plane. Transferring such a tilting snap-action mechanism to a contact system with a rotary contact bridge would detrimentally result in an enlargement of the contact system because of the working volume needed for the tension springs.